Reducing injection loss in drill strings

Abstract

A system and method for transferring wave energy into or out of a periodic structure having a characteristic wave impedance profile at a prime frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, comprising: locating one or more energy transfer elements each having a wave impedance at the prime frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with the imaginary portion approximately equaling zero; and employing the one or more energy transfer elements to transfer wave energy into or out of the periodic structure. The energy transfer may be repeaters. Quarter-wave transformers can be provided at one or more points on the periodic structure with the imaginary portion approximately equaling zero to transmit waves across one or more discontinuities. A terminator can be employed for cancellation of waves. The invention substantially eliminates reflections of the wave energy at the prime frequency by joints between sections of the periodic structure.

What is claimed is:  
     
       1. A system for transferring wave energy into or out of a periodic structure having a characteristic wave impedance profile at a prime frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, said system comprising one or more energy transfer elements each having a wave impedance at the prime frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with said imaginary portion approximately equaling zero. 
     
     
       2. The system of  claim 1  additionally comprising a terminator for cancellation of waves in the periodic structure. 
     
     
       3. The system of  claim 1  wherein reflections of the wave energy at said prime frequency by joints between sections of the periodic structure are substantially eliminated. 
     
     
       4. The system of  claim 1  wherein the periodic structure comprises a structure selected from the group consisting of optical structures, laminated slabs, semiconductor chips, coated lenses, pipes, and geologic formations. 
     
     
       5. The system of  claim 1  wherein said periodic structure comprises a drill string comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       6. The system of  claim 5  wherein said one or more energy transfer elements comprise one or more repeaters. 
     
     
       7. The system of  claim 5  wherein each of said one or more energy transfer elements is located approximately at a longitudinal midpoint of a section of drill pipe or tool joint connection. 
     
     
       8. The system of  claim 5  additionally comprising one or more quarter-wave transformers at one or more points on the periodic structure with said imaginary portion approximately equaling zero to transmit waves across one or more discontinuities in the drill string. 
     
     
       9. The system of  claim 5  wherein each of said one or more energy transfer elements comprises a cross-sectional area approximately equal to said real portion divided by a product of a mass density and a speed of sound of a section of the energy transfer element. 
     
     
       10. A stress wave communication system comprising: 
       a periodic structure for transmitting stress waves at a communications frequency; and  
       a terminator comprising an amplifier having a gain of negative one at the communications frequency.  
     
     
       11. The system of  claim 10  wherein said periodic structure comprises a drill string comprising a plurality of sections of drill pipe and a plurality of sections of tool-joint connections. 
     
     
       12. The system of  claim 10  wherein said terminator additionally comprises a filter to remove frequencies higher than a predetermined frequency above said communications frequency, said filter located between an accelerometer array and a transmitter array. 
     
     
       13. A stress wave communication system comprising: 
       a periodic structure having a characteristic wave impedance profile at a communications frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion; and  
       a quarter-wave transformer having an impedance approximately equal to a square root of a product of an impedance of a member connected to the periodic structure at the communications frequency and said real portion at a point at which said imaginary portion approximately equals zero.  
     
     
       14. The system of  claim 13  wherein said periodic structure comprises one or more drill strings each comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       15. The system of  claim 13  wherein said transformer has a slower wave speed than said periodic structure. 
     
     
       16. A stress wave communication system comprising: 
       a periodic structure for transmitting stress waves at a communications frequency and having a characteristic wave impedance profile at the communications frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion; and  
       one or more repeaters each having a wave impedance at the communications frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with said imaginary portion approximately equaling zero.  
     
     
       17. The system of  claim 16  wherein said periodic structure comprises a drill string comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       18. The system of  claim 17  wherein each of said one or more repeaters is located approximately at a longitudinal midpoint of a section of drill pipe or tool joint connection. 
     
     
       19. The system of  claim 17  wherein each of said one or more repeaters comprises a cross-sectional area approximately equal to said real portion divided by a product of a mass density and a speed of sound of said repeaters. 
     
     
       20. A method for transferring wave energy into or out of a periodic structure having a characteristic wave impedance profile at a prime frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, the method comprising the steps of: 
       locating one or more energy transfer elements each having a wave impedance at the prime frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with the imaginary portion approximately equaling zero; and  
       employing the one or more energy transfer elements to transfer wave energy into or out of the periodic structure.  
     
     
       21. The method of  claim 20  additionally comprising the step of providing a terminator for cancellation of waves in the periodic structure. 
     
     
       22. The method of  claim 20  wherein reflections of the wave energy at the prime frequency by joints between sections of the periodic structure are substantially eliminated. 
     
     
       23. The method of  claim 20  wherein in the locating step the periodic structure comprises a structure selected from the group consisting of optical structures, laminated slabs, semiconductor chips, coated lenses, pipes, and geologic formations. 
     
     
       24. The method of  claim 20  wherein in the locating step the periodic structure comprises a drill string comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       25. The method of  claim 24  wherein in the locating step the one or more energy transfer elements comprise one or more repeaters. 
     
     
       26. The method of  claim 24  wherein in the locating step each of the one or more energy transfer elements is located approximately at a longitudinal midpoint of a section of drill pipe or tool joint connection. 
     
     
       27. The method of  claim 24  additionally comprising the step of providing one or more quarter-wave transformers at one or more points on the periodic structure with the imaginary portion approximately equaling zero to transmit waves across one or more discontinuities in the drill string. 
     
     
       28. The method of  claim 24  wherein in the locating step each of the one or more energy transfer elements comprises a cross-sectional area approximately equal to the real portion divided by a product of a mass density and a speed of sound of a section of the energy transfer element. 
     
     
       29. A stress wave communication method comprising: 
       in a periodic structure transmitting stress waves at a communications frequency; and  
       employing a terminator comprising an amplifier having a gain of negative one at the communications frequency.  
     
     
       30. The method of  claim 29  wherein in the transmitting step the periodic structure comprises a drill string comprising a plurality of sections of drill pipe and a plurality of sections of tool-joint connections. 
     
     
       31. The method of  claim 29  wherein in the employing step the terminator additionally comprises a filter to remove frequencies higher than a predetermined frequency above the communications frequency, the filter located between an accelerometer array and a transmitter array. 
     
     
       32. A stress wave communication method comprising: 
       providing a periodic structure having a characteristic wave impedance profile at a communications frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion; and  
       employing a quarter-wave transformer having an impedance approximately equal to a square root of a product of an impedance of a member connected to the periodic structure at the communications frequency and the real portion at a point at which the imaginary portion approximately equals zero.  
     
     
       33. The method of  claim 32  wherein in the providing step the periodic structure comprises one or more drill strings each comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       34. The method of  claim 32  wherein in the employing step the transformer has a slower wave speed than the periodic structure. 
     
     
       35. A stress wave communication method comprising: 
       providing a periodic structure for transmitting stress waves at a communications frequency and having a characteristic wave impedance profile at the communications frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion; and  
       employing one or more repeaters each having a wave impedance at the communications frequency approximately equal to the real portion of the characteristic wave impedance one or more points on the periodic structure with the imaginary portion approximately equaling zero.  
     
     
       36. The method of  claim 35  wherein in the providing step the periodic structure comprises a drill string comprising a plurality of sections of drill pipe of approximately equal length and a plurality of sections of tool-joint connections of approximately equal length. 
     
     
       37. The method of  claim 36  wherein in the employing step each of the one or more repeaters is located approximately at a longitudinal midpoint of a section of drill pipe or tool joint connection. 
     
     
       38. The method of  claim 36  wherein in the employing step each of the one or more repeaters comprises a cross-sectional area approximately equal to the real portion divided by a product of a mass density and a speed of sound of the repeaters. 
     
     
       39. A method of inserting wave energy into a periodic structure, the method comprising the steps of: 
       determining a point in a periodic structure having a characteristic wave impedance profile at a communications frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, which point has an imaginary portion approximately equaling zero;  
       matching impedance of a wave energy insertion elements to the real portion at said point; and  
       inserting at the point via the wave energy insertion elements wave energy at the communications frequency; and  
       whereby reflections of the wave energy by the periodic structure are substantially minimized.  
     
     
       40. The method of  claim 39  wherein in the inserting step the periodic structure comprises a structure selected from the group consisting of optical structures, laminated slabs, semiconductor chips, coated lenses, pipes, geologic formations, and drill strings.